Macro-quantum mechanistic evaluation of magnetron-sputtered W-coated biochar for the adsorption of diclofenac, crystal violet, and Pb(II) using statistical physics and DFT

Despite a few studies already demonstrating the promising potential of magnetron-sputtered coated materials for enhanced adsorption, the role of the sputtered thin films in the adsorption mechanisms of different classes of contaminants remains challenging. In this study, an in-depth investigation of the adsorption mechanisms of diclofenac (DC), crystal violet (CV), and Pb(II) onto grape waste-derived biochar coated with tungsten thin films via magnetron sputtering at varying current powers was conducted. For this, experimental characterization, statistical physics modeling, and conceptual density functional theory (C-DFT) calculations were combined. Increasing the current power led to an increase in tungsten content and enhanced adsorption performance, reaching adsorption capacities of 798 mg g −1 (DC), 766 mg g −1 (CV), and 684 mg g −1 (Pb(II)). Statistical physics modeling indicated that increasing tungsten content changed the interaction mechanisms, primarily by increasing the number of adsorption energies, and thereby promoting greater adsorbate-adsorbent affinity. Global reactivity descriptors ( µ , η , ω , and χ ) confirmed the trend DC > CV > Pb(II), consistent with the experimental data. It was proposed that DC and CV interact strongly with W-modified biochar via cooperative coordination, hydrogen bonding, π–π and hydrophobic interactions, whereas Pb(II) interacts via outer-sphere and cation–π interactions. Therefore, statistical physics modeling coupled with DFT calculations enables understanding of the contribution of tungsten thin films to adsorption performance and interaction mechanisms, offering valuable insights for designing advanced adsorbents for the removal of organic and inorganic contaminants.